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httpwindow.cpp Example File
network/http/httpwindow.cpp

 /****************************************************************************
 **
 ** Copyright (C) 2010 Nokia Corporation and/or its subsidiary(-ies).
 ** All rights reserved.
 ** Contact: Nokia Corporation (qt-info@nokia.com)
 **
 ** This file is part of the examples of the Qt Toolkit.
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 ** GNU Lesser General Public License Usage
 ** Alternatively, this file may be used under the terms of the GNU Lesser
 ** General Public License version 2.1 as published by the Free Software
 ** Foundation and appearing in the file LICENSE.LGPL included in the
 ** packaging of this file.  Please review the following information to
 ** ensure the GNU Lesser General Public License version 2.1 requirements
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 ** Alternatively, this file may be used under the terms of the GNU
 ** General Public License version 3.0 as published by the Free Software
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 ** packaging of this file.  Please review the following information to
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 #include <QtGui>
 #include <QtNetwork>

 #include "httpwindow.h"
 #include "ui_authenticationdialog.h"

 HttpWindow::HttpWindow(QWidget *parent)
     : QDialog(parent)
 {
 #ifndef QT_NO_OPENSSL
     urlLineEdit = new QLineEdit("https://qt.nokia.com/");
 #else
     urlLineEdit = new QLineEdit("http://qt.nokia.com/");
 #endif

     urlLabel = new QLabel(tr("&URL:"));
     urlLabel->setBuddy(urlLineEdit);
     statusLabel = new QLabel(tr("Please enter the URL of a file you want to "
                                 "download."));

     downloadButton = new QPushButton(tr("Download"));
     downloadButton->setDefault(true);
     quitButton = new QPushButton(tr("Quit"));
     quitButton->setAutoDefault(false);

     buttonBox = new QDialogButtonBox;
     buttonBox->addButton(downloadButton, QDialogButtonBox::ActionRole);
     buttonBox->addButton(quitButton, QDialogButtonBox::RejectRole);

     progressDialog = new QProgressDialog(this);

     connect(urlLineEdit, SIGNAL(textChanged(QString)),
             this, SLOT(enableDownloadButton()));

     connect(&qnam, SIGNAL(authenticationRequired(QNetworkReply*,QAuthenticator*)),
             this, SLOT(slotAuthenticationRequired(QNetworkReply*,QAuthenticator*)));
 #ifndef QT_NO_OPENSSL
     connect(&qnam, SIGNAL(sslErrors(QNetworkReply*,QList<QSslError>)),
             this, SLOT(sslErrors(QNetworkReply*,QList<QSslError>)));
 #endif
     connect(progressDialog, SIGNAL(canceled()), this, SLOT(cancelDownload()));
     connect(downloadButton, SIGNAL(clicked()), this, SLOT(downloadFile()));
     connect(quitButton, SIGNAL(clicked()), this, SLOT(close()));

     QHBoxLayout *topLayout = new QHBoxLayout;
     topLayout->addWidget(urlLabel);
     topLayout->addWidget(urlLineEdit);

     QVBoxLayout *mainLayout = new QVBoxLayout;
     mainLayout->addLayout(topLayout);
     mainLayout->addWidget(statusLabel);
     mainLayout->addWidget(buttonBox);
     setLayout(mainLayout);

     setWindowTitle(tr("HTTP"));
     urlLineEdit->setFocus();
 }

 void HttpWindow::startRequest(QUrl url)
 {
     reply = qnam.get(QNetworkRequest(url));
     connect(reply, SIGNAL(finished()),
             this, SLOT(httpFinished()));
     connect(reply, SIGNAL(readyRead()),
             this, SLOT(httpReadyRead()));
     connect(reply, SIGNAL(downloadProgress(qint64,qint64)),
             this, SLOT(updateDataReadProgress(qint64,qint64)));
 }

 void HttpWindow::downloadFile()
 {
     url = urlLineEdit->text();

     QFileInfo fileInfo(url.path());
     QString fileName = fileInfo.fileName();
     if (fileName.isEmpty())
         fileName = "index.html";

     if (QFile::exists(fileName)) {
         if (QMessageBox::question(this, tr("HTTP"),
                                   tr("There already exists a file called %1 in "
                                      "the current directory. Overwrite?").arg(fileName),
                                   QMessageBox::Yes|QMessageBox::No, QMessageBox::No)
             == QMessageBox::No)
             return;
         QFile::remove(fileName);
     }

     file = new QFile(fileName);
     if (!file->open(QIODevice::WriteOnly)) {
         QMessageBox::information(this, tr("HTTP"),
                                  tr("Unable to save the file %1: %2.")
                                  .arg(fileName).arg(file->errorString()));
         delete file;
         file = 0;
         return;
     }

     progressDialog->setWindowTitle(tr("HTTP"));
     progressDialog->setLabelText(tr("Downloading %1.").arg(fileName));
     downloadButton->setEnabled(false);

     // schedule the request
     httpRequestAborted = false;
     startRequest(url);
 }

 void HttpWindow::cancelDownload()
 {
     statusLabel->setText(tr("Download canceled."));
     httpRequestAborted = true;
     reply->abort();
     downloadButton->setEnabled(true);
 }

 void HttpWindow::httpFinished()
 {
     if (httpRequestAborted) {
         if (file) {
             file->close();
             file->remove();
             delete file;
             file = 0;
         }
         reply->deleteLater();
         progressDialog->hide();
         return;
     }

     progressDialog->hide();
     file->flush();
     file->close();

     QVariant redirectionTarget = reply->attribute(QNetworkRequest::RedirectionTargetAttribute);
     if (reply->error()) {
         file->remove();
         QMessageBox::information(this, tr("HTTP"),
                                  tr("Download failed: %1.")
                                  .arg(reply->errorString()));
         downloadButton->setEnabled(true);
     } else if (!redirectionTarget.isNull()) {
         QUrl newUrl = url.resolved(redirectionTarget.toUrl());
         if (QMessageBox::question(this, tr("HTTP"),
                                   tr("Redirect to %1 ?").arg(newUrl.toString()),
                                   QMessageBox::Yes | QMessageBox::No) == QMessageBox::Yes) {
             url = newUrl;
             reply->deleteLater();
             file->open(QIODevice::WriteOnly);
             file->resize(0);
             startRequest(url);
             return;
         }
     } else {
         QString fileName = QFileInfo(QUrl(urlLineEdit->text()).path()).fileName();
         statusLabel->setText(tr("Downloaded %1 to current directory.").arg(fileName));
         downloadButton->setEnabled(true);
     }

     reply->deleteLater();
     reply = 0;
     delete file;
     file = 0;
 }

 void HttpWindow::httpReadyRead()
 {
     // this slot gets called everytime the QNetworkReply has new data.
     // We read all of its new data and write it into the file.
     // That way we use less RAM than when reading it at the finished()
     // signal of the QNetworkReply
     if (file)
         file->write(reply->readAll());
 }

 void HttpWindow::updateDataReadProgress(qint64 bytesRead, qint64 totalBytes)
 {
     if (httpRequestAborted)
         return;

     progressDialog->setMaximum(totalBytes);
     progressDialog->setValue(bytesRead);
 }

 void HttpWindow::enableDownloadButton()
 {
     downloadButton->setEnabled(!urlLineEdit->text().isEmpty());
 }

 void HttpWindow::slotAuthenticationRequired(QNetworkReply*,QAuthenticator *authenticator)
 {
     QDialog dlg;
     Ui::Dialog ui;
     ui.setupUi(&dlg);
     dlg.adjustSize();
     ui.siteDescription->setText(tr("%1 at %2").arg(authenticator->realm()).arg(url.host()));

     // Did the URL have information? Fill the UI
     // This is only relevant if the URL-supplied credentials were wrong
     ui.userEdit->setText(url.userName());
     ui.passwordEdit->setText(url.password());

     if (dlg.exec() == QDialog::Accepted) {
         authenticator->setUser(ui.userEdit->text());
         authenticator->setPassword(ui.passwordEdit->text());
     }
 }

 #ifndef QT_NO_OPENSSL
 void HttpWindow::sslErrors(QNetworkReply*,const QList<QSslError> &errors)
 {
     QString errorString;
     foreach (const QSslError &error, errors) {
         if (!errorString.isEmpty())
             errorString += ", ";
         errorString += error.errorString();
     }

     if (QMessageBox::warning(this, tr("HTTP"),
                              tr("One or more SSL errors has occurred: %1").arg(errorString),
                              QMessageBox::Ignore | QMessageBox::Abort) == QMessageBox::Ignore) {
         reply->ignoreSslErrors();
     }
 }
 #endif


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Qt 4.6.3